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competency 10/11 > id: tb > Flashcards

id: tb Flashcards

1
Q

mycobacterium tuberculosis

A

obligate aerobic, slow-growing, acid-fast bacilli
waxy cell membrane: does not produce a typical gram-stain response (requires acid-fast stain to visualise)

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2
Q

risk factors for latent and active tb

A
  • residents of prisons, homeless shelters, nursing homes
  • close contact with pulmonary tb pt
  • co-infection with hiv
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3
Q

risk factors for active tb

A
  • children<2yo
  • elderly>65yo
  • malnutrition
  • immunosuppression
  • co-infection with hiv
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4
Q

s/sx of tb

A
  • productive cough
  • hemoptysis
  • fever
  • fatigue
  • night sweats
  • weight loss
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5
Q

radiological findings for tb

A

infiltrates in the apical region, cavitary lesions

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6
Q

pneumonia vs tb, in terms of clinical presentation

A

tb gradual onset (over weeks-months) vs pneumonia acute onset (over hours-days)

tb infiltrates in the apical region vs pneumonia in the middle/lower lobes

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7
Q

indication for latent tb infection screening

A

high-risk group and intent to treat if pos:
- children with recent tb contact
- hiv-infected indiv
- pt considered for tumor necrosis factor antagonist therapy
- transplant pt
- dialysis pt

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8
Q

latent tb diagnosis tests

A
  1. tuberculin skin test
  2. interferon-gamma release assay
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9
Q

tuberculin skin test: pros and cons

A

+ high sensitivity (95-98%)
+ low cost
+ no need to collect blood samples

  • false neg: immunocompromised
  • false pos: envi contact w non-tb mycobacteria, bcg vaxx
  • no universally accepted standards for interpreting results
  • inter-reader variability
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10
Q

interferon-gamma release assay: pros and cons

A

+ performance as good as PPD
+ no false pos in bcg-vaxx indiv
+ minimal cross-reactivity with non-tb mycobacteria
+ results avail within few hrs

  • more ex
  • need for blood samples
  • false neg: immunocompromised
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11
Q

most sg residents are bcg-vaxx: positive tuberculin skin tests >=

A

10mm

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12
Q

prior to treatment for latent tb

A

exclude active tb

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13
Q

latent tb treatment regimen: isoniazid

A

5mg/kg/d
max 300mg daily
x6mths or 9mths(hiv)

  • preferred regimen, especially in pregnancy/lactation/hiv
  • co-adm with pyridoxine (at least 10mg/d) to minimise neuropathy
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14
Q

isoniazid must be co-adm with

A

pyridoxine (at least 10mg/d) to minimise neuropathy(b6 deficiency)

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15
Q

latent tb treatment regimen: rifampicin

A

10mg/kg/d
max 600mg daily
x4mths

  • alt in pt who cannot tolerate isoniazid
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16
Q

latent tb treatment regimen: isoniazid + rifapentin

A

900mg PO weekly
x12wk

  • must be given under DOT
  • not recommended for hiv pt
  • limited clinical experience and evidence to date
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17
Q

standard 6 month active tb treatment

A

intensive phase: 2 months
- daily: RIPE/STM

continuation phase: 4 months
- daily or 3x/wk adm: RI

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18
Q

culture neg

A

does not imply that pt does not have tb
- mycobacterium tb is difficult to grow on culture

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19
Q

pyrazinamide

A

15-30mg/kg daily
max 2g
500mg tab

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20
Q

ethambutol

A

15-25mg/kg/d
max 1.6g
100,400mg tablet

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21
Q

streptomycin

A

IM 10-15mg/kg daily
max 1g

22
Q

rifampicin

A

10mg/kg/d or 3x/wk
max 600mg
100,300mg tab

23
Q

isoniazid

A

5mg/kg/d, max 300mg
15mg/kg 3x/week, max 900mg
150,300mg tab

24
Q

tb drugs that req renal dose adj

A

P,E,STM

25
Q

if unlikely to tolerate PZA eg. elderly or liver disease

A

standard 9-month:
- intensive phase, 2 months, daily RIE
- continuation phase, 7mths, daily or 3x/week RI

26
Q

tb meds exhibit

A

conc-dependent killing > once-daily

27
Q

risk factor for hepatotoxicity

A
  • age>35yo
  • female
  • underlying liver disease
  • concurrent alcohol use
  • hiv
28
Q

sx of hepatotoxicity

A
  • n/v
  • abdominal discomfort or pain
  • unexplained fatigue
29
Q

if have risk factor for hepatotoxicity, lft monitoring

A

at baseline and every 2-4 weeks

30
Q

hepatotoxicity development

A

ALT>3xULN w sx or ALT>5xULN wo sx

31
Q

if hepatotoxicity develops in latent tb tx

A
  • stop tx imm
  • monitor lfts
  • rechallenge with inh when alt improves to <2xULN
  • if pt cannot tolerate inh, switch to rifx4mths
32
Q

if hepatotoxicity develops in active tb treatment

A
  • stop tx imm
  • monitor lfts
  • rechallenge sequentially when lfts normalised and sx resolved
  • if re-challenge fails, may need non-hepatotoxic regimen eg. ETM+FQ+STM
33
Q

EMB can cause

A

visual toxicity
- reduced visual acuity
- reduced red-green colour discrimination

monitor visual acuity and colour discrimination test:
- at baseline for all pt
- monthly in pt w any 2 risk factors: taking etm >2 months, has renal insufficiency eg ckd

34
Q

treatment of tb needs to be prolonged to ensure

A

killing of these slowly growing/semi-dormant org
- if not fully eradicated, might cause relapse

35
Q

for active tb treatment, pt’s ___ should be documented at each visit

A

weight, and have drug dosages adj accordingly

36
Q

adr of RIP

A

gi: anorexia, nausea, abdominal discomfort
- to adm after a light meal or before bedtime
- exclude hepatotoxicity if sx sevre and persisitent

37
Q

adr of all first line anti-tb drugs

A

cutaneous reactions: pruritis - self-limiting

38
Q

as a precaution, rfiampicin should be given with ____ to mothers and neonates born to monthers who have been under treatment w rifmapicin

A

vit K, avoid postpartum hemorrhage
(adr a/w rifampicin is thrombocytopenia)

39
Q

isoniazid metabolism

A

in the liver, through acetylation by N-acetyltransferase
- acetylation rate related to genetic polymorphism: certain pt eg chinese in sg: rapid acetylator phenotype vs indians (slow)

40
Q

isoniazid should not be taken concomittantly with foods

A

rich in tyramine and histamine:
- certain types of fish (tuna)
- cheese and red wine
may give rise to SE such as flushing and headache

41
Q

isoniazid/etm and antacids

A

antacids incr gastric pH and delay absorption of isoniazid/etm - separate from isoniazid/etm ingestion by 2 hrs

42
Q

isoniazid ddi

A

may incr conc of anticonvulsants eg phenytoin and oral anticoagulants

43
Q

which anti-tb drug most effective in eliminating persisters?

A

pyrazinamide

44
Q

pyrazinamide and gout-like sx

A

pyrazinoic acid, principal metabolite of pyrazinamide, inhibits renal tubular secretion of uric acid and results in gout-like sx

45
Q

ethambutol and gout

A

reduce excretion of uric acid by kidney

46
Q

adr of streptomycin

A

ototoxicity, neurotoxicity, nephrotoxicity

47
Q

cure

A

neg sputum smear or culture in last month of tx and on at least one prev occasion

48
Q

tx failure

A

pos sputum bacteriology at or after 5 months of treatment

49
Q

non-conversion of sputum cultures at __ months is a good surrogate marker for risk of relapse

A

2

50
Q
A

competency 10/11 (31 decks)

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